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Tea's health benefits exist, but many claims remain cloudy

Black and green teas have properties that are good for you, but mostly if you brew your own. Herbal teas run hot and cold when it comes to health claims.

By David Levine

9:00 PM EDT, July 26, 2013

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When I was growing up, tea was something I was given by my mother and grandmother as a cure for colds. "Drink some hot tea, and you will feel better. I guarantee it." My choices were pretty simple, Tetley or Lipton.

Today, food stores stock scores of teas. And Americans are drinking it, for taste and for health. According to the Tea Assn. of the USA, Americans drank more than 65 billion servings of tea, or more than 3 billion gallons, in 2011.

Teas are sold to aid in digestion, promote blood circulation, help you sleep better and even make you smarter. There's a caveat: You will usually find labels on the containers saying that "these statements have not been evaluated by the Food and Drug Administration" and that "this product is not intended to diagnose, cure or prevent any disease."

That means consumers have to consider the ingredients in various teas. The research and development manager for the California-based tea company Traditional Medicinals, Zoë Gardner, says there are various ways to consider tea ingredients. In Canada, many of the company's teas have gone through a government licensing process, she says.

"There is traditional-use evidence, such as with the example of senna leaf. Senna leaf was first documented in 900 AD, in Egypt, and has been very well studied and widely used as a laxative in many countries around the world," Gardner says. "Senna is the main ingredient in our Smooth Move tea."

In fact, many of the ingredients found in today's teas have been consumed for thousands of years.

"There are few downsides to drinking tea. Both traditional teas (black and green) and herbal teas are made from plant-based products, which are good for you," says Diane McKay, an antioxidant researcher at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, who conducts research on teas' health benefits. "The best scientific evidence we have on the health benefits of tea is based on research on black and green tea. There has not been as much research on herbal teas."

Dietitian Keri-Ann Jennings adds: "I caution any pregnant or breast-feeding woman to speak to their doctor before drinking any herbal tea. There is a lack of research on the effects of herbal tea on pregnant and nursing mothers."

Here are some common tea ingredients and what is known about their benefits:

Black and green tea

Both contain flavonoids, which are antioxidants. One of these, epigallocatechin gallate (EGCG), is found in abundance in green tea and is thought to help combat the free radicals that can contribute to cancer, heart disease and clogged arteries. The fermentation process that makes black tea converts EGCG into other compounds, but there are compounds in black tea that promote heart health and fight cancer as well.

And tea might make you a wee bit smarter, says Andrea N. Giancoli, a spokeswoman for the Academy of Nutrition and Dietetics. "Both green and black tea contain theanine, an amino acid that can help to improve attention and enhance the ability to learn and to remember."

There are some precautions to consider too. Both black and green tea contain caffeine, which can make some people jittery. However, the average cup of tea has much less caffeine than coffee. According to the Mayo Clinic, an 8-ounce cup of black tea has 14 to 16 milligrams of caffeine. The same amount of green tea has 24 to 40 mg of caffeine. Brewed coffee has 95 to 200 mg of caffeine in a cup.

Black and green tea are the only "real" teas, from Camellia sinensis, a shrub native to China and India. Herbal teas, also called tisanes, are made from steeping flowers, leaves, roots or other plant materials. Some are mixed with actual tea, some not.

Many herbs have been used in traditional and folk medicine for centuries, but few have been formally studied. McKay notes, though, that "does not mean that they are useless. It means we cannot confirm their effects — or the claims that may be made by some of these companies."

It is also unclear whether the quantities of the herbs in commercial herbal tea blends are sufficient to see a health benefit, she says.

Drinking hot or cold tea doesn't seem to make a difference, says McKay, as long as you brew it yourself. "Most of the bottled, ready-to-drink iced teas have such small amounts of tea flavonoids, plus lots of added sugar, that they will not confer the same health benefits as a freshly brewed cup of tea." McKay notes to keep in mind that adding ice dilutes the actual amount of tea you are drinking.

The FDA has cautioned against the use of herbs for infants based on a study published in the journal Pediatrics. The authors of the study found that approximately 9% of infants may be getting dietary botanical supplements and herbal teas during their first year of life and said, "the wide variety of dietary-based supplements and teas given to infants increases the likelihood that some are unsafe."

Chamomile tea

Although often marketed as a way to aid sleep and relaxation, McKay says there is no solid support for that claim. However, don't toss that tea just yet: She says it has heart-healthy antioxidant, anti-inflammatory and cholesterol-lowering benefits.

Hibiscus tea

Hibiscus tea, which has a tart flavor, has shown benefits in humans. In a study published in the Journal of Nutrition, McKay and her colleagues looked at whether the amount of hibiscus in Red Zinger (from Celestial Seasonings) could lower blood pressure in people at risk of hypertension and found that drinking three cups a day did significantly lower blood pressure after six weeks.

Dandelion tea

"It won't hurt you, but it won't help you much either," Jennings says. She notes that dandelions are rich in antioxidants and high in calcium and iron but that the amounts in tea are not enough to be beneficial. "Adding whole dandelions to a salad is the best way to get the good health effects," she says.

Mint tea

Peppermint tea is frequently used to aid digestion, but McKay says there are few, if any, studies of peppermint tea in human subjects. But some people should stay away from mint tea: "Mint teas are bad for people who have gastroesophageal reflux disease," because it could worsen their symptoms, she says.

Ginger tea

Researchers at the University of Maryland note that "ginger has been used to help digestion and treat stomach upset, diarrhea and nausea for more than 2,000 years." Research studies have found that ginger can prevent motion sickness and reduce morning sickness and that it is well tolerated when used in typical doses. At high doses, ginger may cause abdominal discomfort, heartburn and diarrhea.